Implantable stimulator with integrated plastic housing/metal contacts and manufacture and use

ABSTRACT

An implantable stimulator system includes a plastic housing, an electronic subassembly and at least one metal contact. The plastic housing defines an interior chamber and an exterior. The electronic subassembly is disposed in the interior chamber of the plastic housing. The at least one metal contact is integrally formed with the plastic housing, coupled to the electronic subassembly, and accessible from the exterior of the housing. The plastic housing and the at least one metal contact form a sealed structure around the electronic subassembly.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 11/238,240, filed on Sep. 29, 2005, which is incorporatedherein by reference.

FIELD

The invention is directed to implantable stimulators and stimulatorcomponents and methods of making and using the devices. The invention isalso directed to implantable stimulators and stimulator components withintegrated plastic housing and metal contacts, as well as methods ofmaking and using the devices.

BACKGROUND

Implantable stimulators have been developed to provide therapy for avariety of disorders, as well as other treatments. For example,implantable stimulators can be used in neurological therapy bystimulating nerves or muscles, for urinary urge incontinence bystimulating nerve fibers proximal to the pudendal nerves of the pelvicfloor, for erectile and other sexual dysfunctions by stimulating thecavernous nerve(s), for reduction of pressure sores or venous stasis,etc.

As one example, spinal cord stimulation is a well accepted clinicalmethod for reducing pain in certain populations of patients. Implantablestimulators have been developed to provide therapy for a variety oftreatments. For example, implantable stimulators can be used tostimulate nerves, such as the spinal cord, muscles, or other tissue. Animplantable stimulator can include an implanted control module (with apulse generator), one or more leads, and an array of stimulatorelectrodes on each lead. The stimulator electrodes are implanted incontact with or near the nerves, muscles, or other tissue to bestimulated. The pulse generator in the control module generateselectrical pulses that are delivered by the electrodes to body tissue.As an example, electrical pulses can be provided to the dorsal columnfibers within the spinal cord to provide spinal cord stimulation.

BRIEF SUMMARY

One embodiment is an implantable stimulator system that includes aplastic housing, an electronic subassembly and at least one metalcontact. The plastic housing defines an interior chamber and anexterior. The electronic subassembly is disposed in the interior chamberof the plastic housing. The at least one metal contact is integrallyformed with the plastic housing, coupled to the electronic subassembly,and accessible from the exterior of the housing. The plastic housing andthe at least one metal contact form a sealed structure around theelectronic subassembly.

Another embodiment is a method of making an implantable stimulatorsystem. In the method, a plastic housing is formed around at least onemetal contact. The plastic housing defines an interior chamber and anexterior and the at least one metal contact is exposed in the interiorchamber of the plastic housing, as well as at the exterior of theplastic housing. An electronic subassembly is disposed in the interiorchamber of the plastic housing and coupled to the at least one metalcontact. The interior chamber of the plastic housing is sealed.

Yet another embodiment is a method of stimulating tissue. In thismethod, an electrode array is implanted proximate to the tissue. Acontrol module is also implanted. The control module includes a plastichousing defining an interior chamber and an exterior; an electronicsubassembly disposed in the interior chamber of the plastic housing; andat least one metal contact integrally formed with the plastic housing,coupled to the electronic subassembly, and accessible from the exteriorof the housing. The plastic housing and at least one metal contact forma sealed structure around the electronic subassembly. The electrodearray is coupled to the control module using at least one lead.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following drawings. In the drawings,like reference numerals refer to like parts throughout the variousfigures unless otherwise specified.

For a better understanding of the present invention, reference will bemade to the following Detailed Description, which is to be read inassociation with the accompanying drawings, wherein:

FIG. 1 is a schematic exterior perspective view of one embodiment of astimulator system, according to the invention;

FIG. 2 is a perspective view of one embodiment of a component of ahousing of the stimulator system of FIG. 1;

FIG. 3 is a perspective view of one embodiment of another component of ahousing of the stimulator system of FIG. 1;

FIG. 4 is a view of one embodiment of a metal contact assembly,according to an embodiment of the invention; and

FIG. 5 is a schematic overview of components for a system forstimulating body tissues.

DETAILED DESCRIPTION

The invention is directed to implantable stimulators and stimulatorcomponents and methods of making and using the devices. The invention isalso directed to implantable stimulators and stimulator components withintegrated plastic housing and metal contacts, as well as methods ofmaking and using the devices.

Implantable stimulators include a housing that contains the electroniccircuitry and power source that produce electrical pulses that are sentto the electrodes for stimulation of the neighboring tissue. It ispreferable that the electronic circuitry and power source be held withinthe housing in a sealed environment for the protection of the user andthe protection of the circuitry and power source. Once implanted, it isoften preferable that the stimulator can be controlled and/or that theelectrical source can be charged without removing the stimulator fromthe implanted environment.

Previously, implantable stimulators have been made using housings ofmetal (for example, titanium) and/or ceramic. Examples of suchstimulators are found in U.S. Pat. Nos. 6,181,969; 6,516,227; 6,609,029;6,609,032; and 6,741,892, all of which are incorporated by reference.

FIG. 1 illustrates schematically an implantable stimulator system 100,such as for stimulating a spinal cord stimulator. The implantablestimulator system includes a control module (e.g., a stimulator or pulsegenerator) 102, at least one electrode array 104, and at least one lead106 coupling the control module to the electrode array(s). The controlmodule 102 typically includes a housing 114 with an electronicsubassembly 110 and, in at least some embodiments, a power source 112disposed within a chamber in the housing. Preferably, the housing isresistant to moisture penetration into the chamber containing theelectronic subassembly and power source. In some embodiments, water maydiffuse through the housing. Preferably, the diffused water isrelatively pure, without substantial ionic content, as deionized wateris relatively non-conductive.

The housing 114 of the control module is formed of a plastic materialwith metal contacts integrated with the plastic material to connect leadcontacts on the proximal part of the lead(s) 106 with the electronicssubassembly 110 disposed in the housing 114. The plastic housing 114 canbe formed of a plastic material that resists the transport of moistureinto the interior of the housing and is sufficiently sturdy to protectthe components on the interior of the housing from damage under expectedimplantation and usage conditions. Preferably, the material of theplastic housing is a hydrophobic polymer material. The plastic materialof the housing can be a homopolymer, a copolymer formed using two ormore different monomeric units, or a mixture of polymers or othermaterials. Examples of suitable polymer materials include polyolefins,polypropylene homopolymers and copolymers, teflon, andpolyetheretherketone (PEEK). The plastic housing may also includeadditives such as, for example, fillers, plasticizers, antioxidants,colorants, and the like.

The thickness of the walls of the plastic housing may also impact themoisture permeability of the plastic housing. A minimum thickness neededto achieve a particular degree of resistance to moisture transport willoften depend on the material selected for the housing, as well as anyadditives. In general, however, the thickness of the walls of theplastic housing is at least 600 μm and typically ranges from 600 to 1300μm.

Optionally, the plastic housing can be covered, in full or in part, witha coating. The coating can be provided to improve or alter one or moreproperties of the plastic housing including, for example,biocompatibility, hydrophobicity, moisture permeability, leaching ofmaterial into or out of the plastic housing, and the like. The optionalcoating can be a polymer material, metallic material, or organicmaterial. As an example, the plastic housing may be coated with aninorganic material, such as, for example, silicon dioxide, siliconnitride, titanium dioxide, or the like, to reduce moisture permeability.As another example, a silicone coating may be used to improvebiocompatibility. In yet another example, a coating can be applied whichcontains a compound, such as, for example, a drug, prodrug, hormone, orother bioactive molecule, that can be released over time when thestimulator is implanted. (In another embodiment, the plastic housingitself may include such a compound to be released over time afterimplantation.) In some embodiments, the coating includes two or morelayers of the same or different materials. For example, alternatinglayers of inorganic materials can be deposited as a coating to improveresistance to moisture transport through the plastic housing.

The formation of the coating can be accomplished using any methodincluding, for example, dip-coating, sputtering, reactive sputtering,physical or chemical vapor deposition, spray coating, electroplating,electroless plating, and the like. The coating can be applied before theother stimulator components have been assembled with the plastic housingor at any other point in the stimulator manufacturing process includingapplying the coating after the stimulator has been completely assembled.Typically, the coating is non-conductive. A thin conductive coating mayalso be used to increase moisture resistance. Such thin coatings willgenerally not significantly affect the electromagnetic transparency ofthe housing due to the high resistance of the coating to the generationof eddy currents.

FIGS. 2 and 3 illustrated one embodiment of the housing where theplastic housing includes a first portion 120 (FIG. 2) and a secondportion 122 (FIG. 3). The first and second portions 120, 122 can beformed separately and then brought together and sealed to produce thehousing 114 (see FIG. 1). The portions together define a chamber 124into which the electronics subassembly 110 and power source 112 can beplaced and then sealed to prevent or resist moisture transmission intothe chamber. Sealing of the chamber can be accomplished using any methodthat couples the first and second portions 120, 122 together. Suchmethods include, but are not limited to, adhesively coupling theportions together or welding (e.g., laser welding), or otherwiseheating, the seam between the two portions to melt the two portionstogether. It will be understood that the housing illustrated in FIGS. 2and 3 is only one example of a suitable housing. Other housings can beformed using only a single portion or using three or more portions.

In addition, in the illustrated embodiment, the first portion 120defines a compartment 126 into which a proximal end of the lead 106 canbe inserted. The proximal end of the lead 106 has exposed lead contactsthat are connected through the lead to the electrodes 104. These leadcontacts are arranged to make contact with metal contacts 128 disposedin the compartment 126 of the housing 114. The metal contacts 128 areintegrally formed with the first portion 120 of the plastic housing 114.The metal contacts 128 extend from the compartment 126 through thematerial of the plastic housing and into the chamber 124 where the metalcontacts can be coupled to the electronic subassembly 110. In anotherembodiment, one or more (or all) of the metal contacts are exposed on anexterior surface of the housing 114. Generally at least a portion of themetal contacts is embedded in the plastic of the housing. In someembodiments, the lead 106 and metal contacts 128 form a single, integralunit so that the proximal end of the lead 106 forms the metal contactsand is molded into the housing 114. In these embodiments, there is noneed to make a separate connection between lead contacts and the metalcontacts. The lead is connected directly to the electronic subassembly110.

Preferably, when the proximal end of the lead 106 is inserted into thecompartment 126, the lead 106 and housing 114 make contact and seal theentrance to the compartment to resist moisture penetration into thecompartment. In some embodiments, the lead is removable. In otherembodiments, the lead can be permanently coupled to the control moduleusing, for example, adhesive or welding (e.g., laser welding) the leadto the housing.

The integrated plastic housing 114 and metal contacts 128 can be formedby any method. One example of a suitable method includes positioning ametal contact assembly, as described below, inside a mold and theninjection molding the plastic housing 114 or a portion of the plastichousing 114 (e.g., first portion 120) around the metal contact assembly.Other molding methods can also be used. Integrating the plastic housing114 and metal contacts 128 in this manner can enhance the resistance ofthe chamber 124 to moisture penetration because the material of theplastic housing is molded around the metal contacts rather than formingopenings through the housing to insert the metal contacts.

The metal contact assembly can comprise separated individual contacts ora one or more integrated forms containing two or more individualcontacts in each form or any combination of separated contacts andintegrated forms. The individual contacts of an integrated form can beseparated after the molding process. In one embodiment, a metal contactassembly 140, as illustrated in FIG. 4, is used for the molding process.This metal contact assembly 140 provides all of the metal contacts in asingle structure where excess material 142 (indicated by shading in FIG.4) can be removed (for example, by cutting, clipping, or otherwiseeliminating this excess material) after the plastic housing or a portionof the plastic housing is formed around the metal contact assembly.

In another embodiment, the individual metal contacts 128 can be coupledtogether by one or more plastic pieces prior to insert molding the metalcontacts into the housing 102. Preferably, the plastic piece(s) are madeof the same material as the housing. These plastic pieces may be moldedaround the metal contacts and then this pre-molded plastic/metalarrangement can be insert molded into the housing.

The power source 112 is used for generating the stimulation current ormay receive power from an external source. The power source can be anyavailable power source including batteries, such as primary batteries orrechargeable batteries. Examples of other power sources include, but arenot limited to, super capacitors, nuclear or atomic batteries,mechanical resonators, infrared collectors, thermally-powered energysources, flexural powered energy sources, bioenergy power sources, fuelcells, bioelectric cells, osmotic pressure pumps, and the like includingthe power sources described in U.S. Patent Application Publication No.2004/0059392, incorporated herein by reference. In one embodiment, arechargeable power source, such a rechargeable battery or supercapacitors, is used In other embodiments, power may be supplied from anexternal source. Preferably, the power source 112 is resistant tomoisture that may diffuse through the Material of the plastic housing114.

The control module 102 is optionally programmable to allowingprogramming of one or more functions such as, for example, the selectionof electrodes for delivering stimulation, the selection of electrodes asanode or cathode, the amplitude of the stimulation current, the durationof the stimulation current, and the periodicity of the stimulationcurrent. In some embodiments, the control module 102 can be accessedusing a programming unit external to the body of the patient to alter ormodify these functions.

The electrode array 104 typically includes two or more electrodes. Insome embodiments, the electrode array includes four, six, eight, 10, 16,or more electrodes. The electrodes can be in a linear array, forexample, disposed along an electrode lead, or in a two-dimensionalarray, for example, forming two or more columns or rows, or any otherarrangement. Non-limiting examples of suitable electrode arrays areillustrated in U.S. Pat. No. 6,516,227, incorporated herein byreference. In some embodiments, the electrode array is disposed on thedistal end(s) of one or more leads.

The lead 106 includes a set of conductors (for example, one conductorper electrode of the electrode array) within a non-conductive sheathing.Each conductor couples one or more electrodes to each metal contact 128of the control module. Non-limiting examples of suitable controlmodules, electrode arrays, and leads that can be used or modified foruse in the present stimulator system are illustrated in U.S. Pat. Nos.6,181,969; 6,516,227; 6,609,029; 6,609,032; and 6,741,892, all of whichare incorporated by reference.

The electrodes of the electrode array 104 form the anode(s) andcathode(s) of the lead 106. These electrodes can be formed of the sameor different conductive materials. Preferably, the electrodes are formedof materials that do not substantially corrode under the operatingconditions and in the operating environment for the expected lifetime ofthe stimulator. Examples of suitable materials include metals, alloysand other conductive materials such as, for example, titanium, iridium,platinum, platinum iridium, and the like.

The electronic subassembly 110 is disposed in the housing 114 of thecontrol module 102 and provides the electronics used to operate thestimulator and generate the electrical pulses at the electrodes of theelectrode array 104 to produce stimulation of the body tissues. Theelectronic subassembly 110 is coupled to the electrode array(s) 104 viathe metal contacts 128 and lead(s) 106. FIG. 5 illustrates oneembodiment of components of the electronic subassembly and associatedunits. It will be understood that the electronic subassembly can includemore, fewer, or different components and can have a variety of differentconfigurations including those configurations disclosed in thestimulator references cited above. Some or all of the components of theelectronic subassembly can be positioned on one or more circuit boardsor similar carriers within the plastic housing, if desired.

In the illustrated embodiment, a processor 204 is provided to controlthe timing and electrical characteristics of the stimulator. Forexample, the processor can, if desired, control one or more of thetiming, periodicity, strength, duration, and waveform of the pulses. Anyprocessor can be used and can be as simple as an electronic device thatproduces pulses at a regular interval or the processor can be capable ofreceiving and interpreting instructions from an external programmingunit 208 that allows modification of pulse characteristics. In theillustrated embodiment, the processor 204 is coupled to a receiver 202which, in turn, is coupled to the optional antenna 224. This allows theprocessor to receive instructions from an external source to direct thepulse characteristics. The optional antenna, or another antenna, can beused to recharge a rechargeable power source or provide power to thestimulator.

In one embodiment, the antenna 224 is capable of receiving signals(e.g., RF signals) from an external telemetry unit 206 which isprogrammed by a programming unit 208. The programming unit 208 can beexternal to, or part of, the telemetry unit 206. The telemetry unit 206can be a device that is worn on the skin of the user or can be carriedby the user and can have a form similar to a pager or cellular phone, ifdesired. As another alternative, the telemetry unit may not be worn orcarried by the user but may only be available at a home station or at aclinician's office. The programming unit 208 can be any unit that canprovide information to the telemetry unit for transmission to theimplanted stimulator. The programming unit 208 can be part of thetelemetry unit 206 or can provide signals or information to thetelemetry unit via a wireless or wired connection. One example of asuitable programming unit is a computer operated by the user orclinician to send signals to the telemetry unit.

The signals sent to the processor 204 via the antenna 224 and receiver202 can be used to modify or otherwise direct the operation of thestimulator. For example, the signals may be used to modify the pulses ofthe stimulator such as modifying one or more of pulse duration, pulsefrequency, pulse waveform, and pulse strength. The signals may alsodirect the stimulator to cease operation or to start operation or tostart charging the battery. One advantage of a plastic housing is thatplastic is typically more transparent to RF signals than metallic orceramic materials. Thus, in some instances RF signals may be morereliably received or transmitted and received with less power loss whena plastic housing is used. Use of a metal housing, e.g., a titaniumhousing, with a rechargeable battery can be problematic because thehousing can generate eddy currents during inductive recharging. As aresult the rate of recharging is limited as well as the efficiency ofpower transfer. Use of a plastic housing eliminates or reducesgeneration of heat, and can improve the efficiency of transfer of energyinto the rechargeable battery, since no eddy currents result.

Optionally, the stimulator may include a transmitter (not shown) coupledto the processor and antenna for transmitting signals back to thetelemetry unit 206 or another unit capable of receiving the signals. Forexample, the stimulator may transmit signals indicating whether thestimulator is operating properly or not or indicating when the batteryneeds to be charged. The processor may also be capable of transmittinginformation about the pulse characteristics so that a user or cliniciancan determine or verify the characteristics.

The optional antenna 224 can have any form. In one embodiment, theantenna comprises a coiled wire that is wrapped at least partiallyaround the electronic subassembly within the plastic housing.

In one embodiment, a rechargeable battery may be used as the powersource 112 and therefore the power source should be rechargedoccasionally. For example, the rechargeable power source may be arechargeable battery. An external recharging unit 210 may be used toinductively couple the antenna 24 that may be coupled to the receiver202.

The stimulator can be implanted into the body tissue using a variety ofmethods including surgical methods.

The above specification, examples and data provide a description of themanufacture and use of the composition of the invention. Since manyembodiments of the invention can be made without departing from thespirit and scope of the invention, the invention also resides in theclaims hereinafter appended.

What is claimed as new and desired to be protected by Letters Patent ofthe United States is:
 1. An implantable control module configured andarranged for coupling to a lead and electrode array, comprising: aplastic housing defining an interior chamber and an exterior; anelectronic subassembly disposed in the interior chamber of the plastichousing; and a plurality of metal contacts integrally formed with theplastic housing, coupled to the electronic subassembly, and accessiblefrom the exterior of the housing, wherein the housing is formed aroundthe plurality of metal contact such that the plastic housing and theplurality of metal contacts form a sealed structure around theelectronic subassembly.
 2. The implantable control module of claim 1,wherein the plastic housing defines a compartment that is accessiblefrom the exterior of the plastic housing through an opening.
 3. Theimplantable control module of claim 2, wherein the plurality of metalcontacts extend from the compartment into the interior chamber, andwherein a portion of the plurality of metal contacts disposed in thecompartment are directly coupleable to the lead.
 4. The implantablecontrol module of claim 1, wherein the plastic housing comprisespolyetheretherketone.
 5. The implantable control module of claim 1,wherein the plastic housing comprises walls having, a thickness in arange of 600 to 1300 μm.
 6. The implantable control module of claim 1,wherein the plastic housing comprises a hydrophobic polymer material. 7.The implantable control module of claim 1, further comprising a coatingdisposed on at least a portion of the housing.
 8. The implantablecontrol module of claim 7, wherein the coating comprises silicondioxide, silicon nitride, or titanium dioxide.
 9. The implantablecontrol module of claim 7, wherein the coating comprises silicone. 10.The implantable control module of claim 7, wherein the coating comprisesa drug, prodrug, or hormone configured and arranged for release overtime when the control module is implanted.
 11. The implantable controlmodule of claim 1, wherein the plurality of metal contacts areintegrally formed with the housing by injection molding at least aportion of the plastic housing around a metal contact assemblycomprising the plurality of metal contacts.
 12. A method of making animplantable control module, the method comprising: molding a plastichousing of the control module around a plurality of metal contacts,wherein the plastic housing defines an interior chamber and an exteriorand the plurality of metal contacts are exposed in the interior chamberof the plastic housing and are exposed at the exterior of the plastichousing; disposing an electronic subassembly in the interior chamber ofthe plastic housing; coupling the electronic subassembly to theplurality of metal contacts; and scaling the interior chamber of theplastic housing, wherein the housing is molded around the plurality ofmetal contacts such that the plastic housing and the plurality of metalcontacts form a sealed structure around the electronic subassembly. 13.The method of claim 12, wherein forming a plastic housing comprisesinjection molding a plastic housing around a metal contact assembly andforming the plurality of metal contacts from the metal contact assembly.14. The method of claim 13, wherein forming the plurality of metalcontacts comprises removing material from the metal contact assembly toform a plurality of metal contacts.
 15. The method of claim 13, whereinforming a plastic housing comprises forming at least two housingportions and wherein sealing the interior chamber of the plastic housingcomprises sealing the at least two housing portions together.
 16. Themethod of claim 15, wherein forming at least two housing portionscomprises forming one of the housing portions around the metal contactassembly.
 17. The method of claim 12, further comprising disposing acoating over at least a portion of the housing.
 18. The method of claim17, wherein the coating comprises silicon dioxide, silicon nitride,titanium dioxide, or silicone.
 19. The method of claim 17, wherein thecoating comprises a drug, prodrug, or hormone configured and arrangedfor release over time when the control module is implanted.
 20. Themethod of claim 17, wherein disposing a coating comprises formingmultiple coating layers on the housing.